Field of the Invention
The present invention relates to a plugged honeycomb structure and a manufacturing method of the plugged honeycomb structure, and more particularly, it relates to a plugged honeycomb structure which can effectively inhibit a rise of a pressure loss generated due to deposition of particulate matter on partition walls while lowering the highest temperature during regeneration, when the plugged honeycomb structure is used as a filter such as a DPF, and a manufacturing method of the plugged honeycomb structure.
Description of Related Art
An exhaust gas discharged from an internal combustion engine such as a diesel engine, each type of combustion device or the like includes a large amount of particulate matter (hereinafter also referred to as “PM”) mainly composed of soot. When this PM is discharged as it is into the air atmosphere, an environmental pollution is caused. Therefore, in an exhaust system for the exhaust gas, a particulate filter to trap the PM is mounted. An example of the particulate filter is a diesel particulate filter (DPF) for use in purification of the exhaust gas discharged from the diesel engine.
In such a DPF, there is used, for example, a honeycomb structure having porous partition walls defining a plurality of cells which become through channels for the exhaust gas. In this honeycomb structure, plugging portions to plug open ends of cells are disposed in the open ends of the predetermined cells in an end face on an outflow side of the fluid and the open ends of the residual cells in an end face on an inflow side of the fluid, and hence this honeycomb structure is utilized as a plugged honeycomb structure. Hereinafter, a particulate filter such as the DPF in which the plugged honeycomb structure is used will generically be referred to as “a honeycomb filter” sometimes.
As such a plugged honeycomb structure, for example, a plugged honeycomb structure has been suggested in which a porous trapping layer is further disposed on the surface of a partition wall base material of a honeycomb structure (e.g., see Patent Documents 1 and 2). Hereinafter, “the plugged honeycomb structure in which the trapping layer is disposed on the surface of the partition wall base material of the honeycomb structure” will be referred to as “the plugged honeycomb structure including the trapping layer” sometimes. Such a trapping layer has a larger specific surface area than the partition wall base material of the honeycomb structure.
In a honeycomb filter such as the DPF, a pressure loss gradually increases due to the PM deposited in the filter with an elapse of time, and hence the PM deposited in the honeycomb filter is periodically burnt and removed to regenerate the filter sometimes. For example, as a method of regenerating the DPF, a regenerating method is known in which a temperature of the exhaust gas discharged from the engine is raised to heat the DPF by use of the exhaust gas at a high temperature. An example of a method of raising the temperature of the exhaust gas is a method in which by post jetting to temporarily excessively jet a fuel in a latter half of an explosion stroke or in an exhaust stroke, the excessive fuel is burnt to raise the temperature of the exhaust gas.
[Patent Document 1] JP-A-2012-201542
[Patent Document 2] JP-A-2012-200649